The present invention relates generally to differential gear mechanisms and, more particularly, to an improved arrangement for retaining the cross shaft within the differential case.
As is known, differential gear mechanisms are incorporated into the drive system of motor vehicles for permitting relative rotation between the wheels, while concomitantly supplying motive power thereto. As shown in FIG. 1, a conventional differential gear mechanism 10 typically includes an outer housing 12 and a differential carrier or casing 14 that is rotatably supported by bearings 15 for rotation within outer housing 12. Differential casing 14 has an enlarged interior chamber 16 and a pair of polar apertures 18 in communication therewith. An elongated cross shaft 20 extends through interior chamber 16 and has its opposite ends disposed within polar apertures 18. In addition, a pinion gear 22 is rotatably supported on each end of cross shaft 20 within interior chamber 16. Moreover, a pair of side gears 24 are also retained within interior chamber 16 and are each arranged in meshed engagement with pinion gears 22. Differential casing 14 is open at its opposite axial ends for receipt of a pair (i.e., left and right) axle half-shafts 26 which, in turn, are drivingly coupled to the wheels. As is known, each axle half-shaft 26 is fixed (i.e., splined) with a respective one of side gears 24 for rotation about an axis of rotation, denoted as Axis "A". A large ring gear 28 is secured to differential casing 14, such as by bolts 30 and is rotatably driven by a drive shaft (not shown) of the motor vehicle for delivering power through differential gear mechanism 10 to axle half-shafts 26 in a conventional manner.
To retain cross shaft 20 within differential casing 14, a locking pin 32 is inserted through a pair of alignable cylindrical bores 34 and 36 formed in differential casing 14 and cross shaft 20, respectively. As seen from FIGS. 1 and 2, cylindrical bore 36 extends through, and is symmetrical relative to, a central longitudinal axis "B" of cross shaft 20. However, it is known that during severe wheel slip situations, pinion gears 22 exert relatively large torque loads on cross shaft 20 which attempt to rotate cross shaft 20 within polar apertures 18. As such, the torque loading is transferred from locking pin 32 to differential casing 14 as a shear load. Accordingly, the cross-sectional area of locking pin 32 must be able to withstand such shear loads for retaining cross shaft 20 within differential casing 14. Unfortunately, if the torque loading causes locking pin 32 to shear, then cross shaft 20 would be free to slide out of differential casing 14, whereby differential gear mechanism 10 would become inoperative.
It is also known that conventional cross shaft retaining arrangements commonly require additional machining operations and/or an increase in the number of components, each of which tend to increase the overall complexity and cost of the differential gear mechanism. Moreover, special tools are often required to assemble and disassemble such differential gear mechanisms which are cumbersome to use and/or require an excessive amount of manual manipulation. Accordingly, it is the purpose of the present invention to solve these and other problems typically associated with conventional locking arrangements by providing an improved means for retaining a cross shaft with the differential casing of a differential gear mechanism.